This invention relates to a vehicle incorporating a movable implement associated therewith, and more particularly to means for providing a coordination of movement in a stick arm and the implement associated with the vehicle.
In vehicles incorporating a raisable and lowerable boom, a stick arm pivotally mounted to the boom, and an implement pivotally mounted to the stick arm, it is necessary that the movements of the stick arm and implement be properly coordinated under various operating conditions. This is generally accomplished by means of hydraulic cylinders and an associated hydraulic control system for the cylinders. In general, one cylinder is extendable and retractable to pivot the stick arm relative to the boom, and another cylinder is extendable and retractable to pivot the implement relative to the stick arm. Yet another cylinder interconnects the frame of the vehicle and the boom for overall raising and lowering of the boom.
In a typical system of this type incorporating, for example, a rock-breaking implement, if the stick arm cylinder is actuated in one direction, the entire assembly made up of the stick arm, rock-breaking implement, and implement cylinder, is pivoted as a unit relative to the boom. Thus, under such conditions, the tooth of the rock-breaking implement changes in attitude relative to, for example, a vertical, or a horizontal surface on which the tooth works. It has been found desirable that the attitude of such implement and tooth thereof remain generally the same relative to such vertical or horizontal surface during the swinging of such assembly due to actuation of the stick arm cylinder. It will be understood that during the normal operation of such an apparatus, in order to achieve a generally unchanging attitude of the implement relative to such vertical or horizontal earth surface, the operator of the vehicle must actuate the implement cylinder in a very precise manner. This may not always be feasible or convenient, due to, for example, poor operator visibility or difficulty in simultaneously operating the controls of the stick arm cylinder and implement cylinder.
Of general interest in this area are U.S. Pat. No. 3,179,120, incorporating a flow divider for dividing flow between a boom cylinder and an implement cylinder. Also, of general interest in this area are U.S. Pat. No. 3,175,580, and U.S. Pat. No. 2,998,891, each incorporating spool-type control valves for achieving bucket leveling.